These non-word noises were never normally written down, mainly because it was difficult to work out how to spell them. How would you spell the throat-clearing noise? Ways have been found of writing them down, though. And some of them are new arrivals in the Cambridge Dictionary.
The two mentioned above are transcribed conventionally as ahem and tut (UK) or tsk. Other paralinguistic noises in English include psst, used to attract someone’s attention discreetly; sh (or shh, or ssh, or shush) to call for silence; and phew (or whew) to express a feeling of relief, or of feeling too hot. Different languages transcribe a sneeze in different ways (in English atishoo or achoo, but atchim in Portuguese).
There are also some more modern paralinguistic noises. Air kissing, a phenomenon of modern celebrity culture where two people greet each other by moving their faces together without actually touching, can be written down as mwah, a kind of soft kissing noise. And Homer Simpson’s d’oh has entered the dictionary as an expression that indicates you, or someone else, has said or done something stupid.
The interesting thing about paralinguistic noises is that people don’t always associate the written form of the noise with the actual sound – perhaps because the spelling is so arbitrary. And when they see it written down, for example in a comic strip, they give it a more conventional pronunciation using regular English sounds. So, for example, people will now say brr! when they feel cold, even though the spelling was designed to represent that involuntary wobbling of the mouth when you’re shivering with cold. And ouch, representing a cry of pain, is frequently pronounced as a word – though obviously only if the pain is not too severe!